The present invention relates generally to safety systems for syringes, and more particularly to a dental syringe for a medical cartridge that includes a shield for selectively covering the needle of the syringe after medication is dispensed from it.
Medication is often dispensed using a medical cartridge, such as an ampoule or syringe, received in a syringe holder or adapter. The cartridge generally includes a barrel having a piston in one end and a penetrable seal or rubber stopper on the other end. The syringe adapter generally is a hollow body having a cavity for receiving the cartridge therein. The body may have an open end allowing axial loading of a cartridge into the cavity, or it may include an opening for side loading.
A double-ended needle may be provided on one end of the body for penetrating the seal on the cartridge received in the cavity to allow delivery of medication in the cartridge through the needle into a patient. A plunger assembly may be provided on the other end of the body for engaging and moving the piston in the cartridge to deliver medication and/or to aspirate the cartridge. Alternatively, the cartridge itself may include a needle instead of a penetrable seal, and the body may simply have a hole through which the needle may be directed when the cartridge is received in the cavity.
Because of the threat of communicable diseases, a number of syringes and adapters have been proposed to prevent accidental needle sticks or inadvertent reuse of needle devices. Many of these devices, however, are not easy to use or are complicated to manufacture, resulting in less effective disposable syringe devices. For example, retractable needle devices have been proposed that allow the needle of the syringe to be withdrawn into the barrel of the syringe after medication is dispensed from it. Such devices, however, generally require customized cartridges and cannot accommodate conventional cartridges.
Extendable shield devices have also been proposed that include a slidable shield mounted on a body for receiving a cartridge. The shield may be directable between a retracted position exposing the needle for use, and an extended position substantially covering the needle for disposal. Some devices allow the shield to freely slide back and forth between the retracted and extended positions. Such devices, however, may result in a shield that may inadvertently advance towards the extended position during use, possibly interfering with an injection, or that may expose the needle after use, risking an accidental needle stick.
To protect against this, the shield and body may include cooperating elements, such as detents and detent pockets, that automatically lock the shield when advanced to the extended position. Thus, the shield may be substantially permanently locked, covering the needle to facilitate safe disposal. These cooperating elements may work well for a single use device, but if multiple injections need to be given to a patient, it may be desirable to selectively cover the needle between injections, but eventually lock the shield in the extended position for final disposal.
Accordingly, it is believed that a syringe adapter that allows selective extension or retraction of a needle shield would be considered useful.
The present invention is directed to self-shielding syringes, such as an aspirating dental syringe, and to methods of using such a syringe. In one embodiment, the syringe includes a body having proximal and distal ends and a cavity therein for receiving a medicine cartridge, the distal end having an opening through which a needle may extend. A shield is slidably attached to the body that is slidable between a retracted position wherein a needle extending from the distal end of the body is exposed through a distal end of the shield, and an extended position wherein the needle is substantially covered by the shield. A cooperating detent and detent pocket is provided on the shield and body for releasably holding the shield in the extended position. A latch is also provided for locking the detent in the detent pocket for preventing subsequent retraction of the shield from the extended position.
A needle may extend from the distal end of the body. The needle may be molded directly into the distal end of the body, or may include a threaded hub for attaching the needle to a mating threaded hub on the body. More preferably, the needle includes a double-ended needle having a first end extending distally from the body and a second end extending into the cavity for penetrating a seal on a cartridge received in the cavity.
The proximal end of the body may include an opening for directing a cartridge axially therethrough into the cavity. A plunger assembly may then be provided on the proximal end of the body for engaging a piston in the cartridge received in the cavity for delivering a medication in the cartridge through the needle. The plunger assembly may include a plug that is attachable to the proximal end of the body for encapsulating the cartridge in the cavity, and a plunger slidably attached to the plug.
In a preferred embodiment, the detent is molded on the shield and the detent pocket is molded into the body. The detent is preferably deflectable radially outward for withdrawing the detent from the detent pocket to allow retraction of the shield. For example, a lever may be molded on the shield having the detent on a first end thereof, the lever being pivotable for deflecting the detent radially outward.
In first embodiment, the latch may be a hinged member on a second end of the lever opposite the detent, the hinged member being receivable in a pocket in the shield for preventing subsequent pivoting of the lever. In a second embodiment, the latch may be a hinged member on the shield, the hinged member engageable with the lever to prevent subsequent pivoting of the lever. In a third embodiment, the latch may be a hinged member on a second end of the lever opposite the detent, the hinged member being engageable to the first end of the lever for preventing subsequent pivoting of the lever.
In another embodiment of the present invention, a syringe is provided that includes a three-position shield. The syringe includes a body having proximal and distal ends and a cavity therein for receiving a medicine cartridge, and a shield that is slidably attached to the body. A needle cannula is provided on the distal end of the body having a proximal portion extending proximally into the cavity, and a distal portion extending distally beyond the distal end of the body. A plunger assembly is provided on the proximal end of the body for distally directing a piston in a cartridge received in the cavity to deliver medication from the cartridge through the needle. Cooperating detents and detent pockets are provided on the body and shield to temporarily hold the shield in a retracted position wherein the distal portion of the needle is exposed, to temporarily hold the shield in an intermediate guarded position wherein the distal portion of the needle is substantially covered, and to substantially permanently lock the shield in a fully extended position distally beyond the intermediate position.
More preferably, the cooperating detent and detent pockets include a set of detents molded on the shield. Proximal, intermediate, and distal sets of detent pockets are molded into the body, the intermediate set of detent pockets having sloping proximal and distal edges for facilitating sliding the detents out of the intermediate set of detent pockets to direct the shield towards one of the retracted and fully extended positions. The distal set of detent pockets preferably have substantially blunt proximal edges for preventing proximal movement of the shield once the set of detents are received in the distal set of detent pockets.
In accordance with another aspect of the present invention, a method is provided for injecting a medication into a patient using a syringe having a slidable shield thereon in a retracted position wherein a needle of the syringe is exposed. Medication is injected from the syringe into a patient through the needle. The shield is then advanced axially until cooperating detents on the syringe engage to secure the shield in an extended position that substantially covers the needle.
If desired, the cooperating detents may be disengaged to allow retraction of the shield to expose the needle before engaging the latch. Additional medication may be injected from the syringe into the patient through the needle, and then the shield may be advanced again to the extended position. When it is desired to dispose of the syringe, a latch may be engaged to substantially permanently lock the cooperating detents in engagement, thereby substantially permanently locking the shield in the extended position.
In a preferred embodiment, the syringe includes a body and a shield having the cooperating detents thereon, as described above. When it is desired to disengage the cooperating detents, a deflectable portion of the shield may be directed radially outward to disengage detents on the deflectable portion from cooperating detents on the body. More preferably, the deflectable portion is a lever molded to the shield, which may be engaged with the latch to prevent subsequent deflection of the lever. With the shield substantially permanently locked in the extended position, covering the contaminated needle, the syringe may then be disposed of. Thus, a syringe in accordance with the present invention may substantially reduce the risk of accidental needle sticks during use and disposal of the syringe.
Other objects and features of the present invention will become apparent from consideration of the following description taken in conjunction with the accompanying drawings.